Telephone system



7 Sheets-Sheet 1 June 5, v

- R. MERCER El' AL TELEPHONE SYSTEM w NN! Imran nrs H NQ 9m) P 4 2 w W 4 v w iw H 0 w Y N 1 m lll Elch-1rd Mercer, LJzZZzam .'faulmand Frank Tennh dunes, 192s.

' 1,672,225 R MERCER Er AL TELEPHONE SYSTEM Filed oct. 4, 1924 7 sheets-sheet 2 \o :N EN Nl DD l w --Imrfmr's--- Ezcharcf Nemen, Lllham I'LFaul'eTCandFrank Tauch .im s, 192s.

` R. MERCER ET AL TELEPHONE SYSTEM www. NMS Nw m2 .QU NY n M\\k v w%\ L.om mlmmmnw d .Tv

Imran DPslhard Mercer, M1111 1,57?, and Frank Tauch HTI-T June 5, 1928. 1,672,225

R. MERCER Er AL TELEPHONE SYSTEM V `Filed oct. 4, 1924 l 'r sheets-sheet 4 Rzchard Mercer, Dll'llhm H Faillanu Frank Tauch Janes, im

R. MERCER ET'AL TELEPHONE sYsTEu Filed oct'. 4, A1924 7 Sheets-$heet 5 f IUen DFS Elcha'rd Mercer, lu'llham H Faul; and Frank Tauch June 5, |928. 1,672,225

R. MERCER rrr-Al.

TELERHONE SYSTEM Filed O01.. 4, 1924 Sheets-Sheet 6 fr-Ewa Ezphard marcar, Dlrllam H Faulmdlrank Tenth June 5, 1928.

l R. MERCER Er AL TELEPHONE ssmi 7 Sheet s-Sheet 7 Filed Oct. 4, 1924 Imran uns chard FIer'cer, Lu'zlllm HEILIEH; and Frank TEnCh Y' Patented June 5, 1928.

UNITED .sra-Tias g 1,572,225- PATENT- OFFICE.

RICHARD MERCER, 0F HARROW, WILLIAM H. PAULETT, OFy WANDSWORTHLLONDON, AND FRANK TEN'CH, OFv WEST NORW'OOD, LONDON, ENGLAND,` ASSIGNORS, BY MESNE ASSIGNMENTS, TO AUTOMATIC ELECTRIC INCL, OF CHICAGO, ILLINOIS,

CORPORATION OF DELAWARE.

TELEPHONE SYSTEM.

Application filedoefotei 4. 1924,5ena1 No., 741,550, and in `Great Britain october 13, 1923.

IThepresent invention concerns improvements in or relating tl automatic or semiautomaticl telephone systems andV themain object of the invention may be stated broadly to be the provision of improved circuit ar'- rangements rpermitting ldialling to take.

place over both speaking leadsin series and supervision to be effected over the speaking leads independently. Underthese circumstances the admitted .advantages of loop dialling may be combined witlrthose of supervision as employed in standard manual practice and by means oli the invention, Without any serious complication of the switches and other apparatus.

According to one feature of the invention setting and supervision are effected over the same leads under different circuit conditions andI the setting conditions-are maintainedl adapted to close a point in` the energizing circuit ofthe line relay of an automatic switch which in turn causes a second point to be closed independently of lsaid springs so that the line relay is connected in a loop circuit during dialling. ranged that the circuit forthe line relay is not completed until the operator throws her dialling key so that there is vno danger of false impulses being s ent owing to careless plugging in.

A further lfeature of theinvention is that a switching device is provided arranged to be automatically operated after impulses have been transmitted andr before a supervisory signal has been sent to replacethe metallic circuit across the speaking leads used for dialling by a circuit including the supervisory apparatus. l Still another feature of the invention is that the connections over which battery is fed forward to or in the direction of a called Itis further arexchange.

party duringy conversation are maintained open by a relay initially energized ina local circuit, maintainedv renergized by battery fed back -from succeeding switches over the two speaking4 conductors', in series during the setting of lsaid switches and deenergized when the connection Lis extended as far as possible towards thek wanted line.

The circuit of this relay is preferably maintained intact .while the connection is being extended` through vintermediate switches by the provision of makebefore break springs on the wiper relays of the various intermediate selectors. f

These and other features not specifically mentioned at thispoint will be more fully understood fromthe following description taken in conjunctionwith the accompanying drawings. It will be understood however that the embodiment of the invention now to be'described is given by way of example only and that considerable:modifications in the circuit details might be made by those skilled in the art without exceeding the scope of `the invention... f

Referring now to the drawings, VFig. lshows a localvselector embodying the invention.

Fig. 2 an inc'omingselector,

Fig. 3 an intermediate selector, and

Fig. 4 a connector. f

It is intended that these four figures should be placed together with the corresponding lines in alignment in order that the connection which is about to'be described may be traced out.

Fig. 5 shows the apparatus provided at a complaint or while f v Figs. 6 and 7 show respectively anoperators cord vcircuit and.r selector, such as would be used for extending a connection from an Al operator over a'trunk line and over lautomatic switches `to a distantv In the connection between two` automatic subscribers it will be considered that'only one digit is used for exchange selection, this digit operating the local selector which then seizes a trunk line leading to the incoming Yselector from which the connection is then extendedover an intermediateselector tov a connector.` It will be realized that with inquiry operators position,

such a train of switches Ithe number dialled by the subscriber will comprise 5 digits and that the system therefore might consist oi?- 10fexchanges eachof 10,000 lines capacity. It willI be realized however `that the rinvention` is in noway limit-ed to a system of this size, and that additional switches of one or other of the various types described may be added as necessary and conversely one or more of the switching stages may be omitted.

Considering now the setting up of a connection, yit will 'fbe assumed that the viirst selector shown in Fig. 1' is accessible over the usual subscribers line switch, which', bei-ng well known in the art, is not shown. then the line switch" seizes the selector shown: and' switch'esth'rough, a Acircuit is completed overV conductors 1 and 2t and the subscribers =1oop for `the" upper' and lower windings .of the line relay 5. Relay iupon operating, at its armature 6A completes aciral"bridge across the outgoing trunk line which' latter operation is however without effect at this point. Rel-*ay 8 lenergi'zes and atarmature `9 connects earth to release ktrunk conductor?) so as to 'maintain the line switch operated and' at armature '10' prepares the -ifmpulsing circuit. The switch is ynow in condition to respond to the first digit dialled by t'hesubscriber. Whenv this operation takes' place, a number of interruptions will *be `producedA yin the circuit of line relay 5 and it will deenergize acorresponding numfber of times; upon' each deenergi'zation a circuit is completed from earth, armature A6 and its back contact, armature 10 and its "front contact, armature 15I and its back contact, vertical magnet 16 to battery. A branch of this circuit also extends through the winding of relay 1'1, Iwhich thereupon energizes and being slow to release lremains energized rthroi-rghout' the 'train yof impulses. the operation of vertical magnet 16, the switch shaft and wipers are raised a number of steps corresponding -to the digit dialled. The operation of relay 11 completes a circuit atarmature 13' for the upper winding off relay 17, and lat armature 14 completes a low resistance bridge across the trunk condoctors which latter operation is, however, without effectat ythis point. Relay 17 upon operating, at lits armatures 18 aand 19 completes a locking circuit for itself, which extends as itollowszhbattery, resistance, normally closed springs `controlled by armature k28, armature 18 and its front Contact, lower winding of relay 17 front contact `andarmature 19, front contact andarmature 7, normally closed springs controlled by armature '31 to earth. This locking circuit becomes effective when the sending of impulses ceases, land thus relay 1'7 which is held up over its `upper winding during the transmis sion of impulses is then'` held locked over its lower winding. Relay 11 also atn armature 12 completes a circuit for stepping relay"21` Y' which becomes effective when the ofi nonmal contacts 26v close on the first vertical step of the switch. This circuitextends as follows: earth, `front contact and larmature 9, armature 12 and its front Contact, armature 29 and its back contact, interrupter contact 25, off normal contacts 26, winding of relay 21 to battery; Relay' 21 therefore operates, at armature 22 completes ay locking circuit forr itself, and at armature 23' prepares a circuit for the rotary-magnet 24. Upon the deenergization of relay 1.1, a circuit' is completed at armature 12fand its back' contact for rotary magnet 24 whereupon the switchL wipers are rotated intoengagement `'with the first set of bank contacts. The rotary magnet 24 by opening its interruptor 'contact 25 breaks the locking `circuit ot relay 21 so 'thatjthis deenergizes cuit for relay 8f and" at armature 7 prepares v and opens the circuitv of the rotarymagn'et at ,armature 23.; If the test wiper 41 now .fiinds earth on the Contact with which it is `iin engagement, a circuit is 4again completedl for stepping relay 21 and onV the opera-tion of armature 23 vthe switch takes a further step. This 'cycle continues vuntil test wiper' 41 reaches a contact whichis not earthed, for

instance, the contact 44, whereupon switching relay 27 is no longer short circuited, and energizes in series with steppingreilay 21, which ishoweyer not operated at this time. Relay A27 at armature connects test wiper 41through to release trunk conductor 3 and opens the initial energizing circuit of relay 21, at armature 30 prepares the circuit. for the supervisory relays 32 and. 36', at armature 15 opens the circuit of the ,vertical magnet and at armatures 28 and 31 -d'isconnectsthe lower winding of relay A17 l from the lo-al battery and earth connections and connects it over the trunk conductors 51 and '52 and back contact and armature 78 tothe line relay 530i the incoming selector shown in Fig. 2. 'As the armatures 28' and 31 control make-before-break springs, there is no discontinuity when theyoperate and relay 17 is'thus maintained energized. lay now energizes and completes a circuit for relay 56 thus preparing the vswitch Lshown in Fig. 2 is substantially similar to that ot thelocal selector.. but as one or two important differences arise, this operation will be traced through in detail. When the tarily deenergized a number of times andv thereby operates its armatures 6 and 7. At

armature 6 the usual circuit is completed for the series relay 11 and this operates to main` tain relay 17 energized at its armature 13 and atarmature 14 to connect the trunkconductors together so as to improve the im-v pulsing circuit. The verticalmagnet 1.6 cannot now be operated since armature 15 has left its backcontact and relay 27 cannot be again short circuited owing to the operation of armature 29. The circuit for'repeating impulses to the incoming selector extends as follows: earth, lower winding of relay 53, trunk conductor 52, contact 43, wiper ,40, armature 31 and its front contact, armature 7 and'its front contact, armature 14 and its front contact, front contact and armature 2S, wiper 39, contact 42, trunk conductor 51, back contact and armature 78, upper winding of relay 53 to battery. A similar number of interruptions is thus produced in the circuitvof the line relay 53 of the incoming selector, and this therefore at armature 54 completes a circuit overarmature 58 and its front contact for series relay 59 and in parallel over armature 63 and its back contact to the vertical magnet 64. Series relay 59 acts in a similar manner to the series relay 11 of the first selector, and at armature 60 prepares a circuit for stepping relay 70, at armature 61 completes a circuit for the upper winding of relay 65 and at armature 62 connects the outgoing trunk conductors together. Relay 65 upon operating at armatures 67 and 68 locks itself up to local battery and earth connections over the normally closed springs controlled by armatures 77 and 81 of switching relay 76 and at armature 66 shunts armature'7 8 for a purpose which will be appreciated short-ly. The incoming se* lector is thus stepped up to the desired level f by the operation of the vertical magnet 64 and when off normal contact closes on the first step, a circuit is completed for stepping relay 70 which at armature 71 completes a locking circuit for itself, and at armature 72 prepares a circuit for the rotary magnet 73. on the termination of the series of impulses, armature 60 engages its back contact and the hunting opera-tion of the switch is initiated and continues under the control of interi rupter contact 74 in the manner described in connection with the first selector.` Then wiper 94 engages a contact which is not earthed, for instance contact 97, switching relayy 76 is energized in series with stepping relay 70 and at its armature 77 and81 transfers the locking circuit throughv the lower winding of relay 65 to the line relay 104 of the intermediate selector shown in Fig. 3.

lay 53.

Consequently when relay 59 deenergizesv Relay 7 6 moreover at its armature 63 opens the circuit of the'vertical magnet` to prevent this being further operated, at armature 80 prepares a circuit for the supervisory relays 82 and 88, at armature 79 places earth yfrom armature 57 on test wiper 94, and at armature 78 opens a point in the circuit of line 're- Since however this armature has been shunted by armature 66 of relay 65, which is still operated, relay 53 remains operated and consequently relay 17 of the local selector.

The intermediate selector shown in Fig. 3v is substantially thensameas the standard selector .and only differs ltherefrom in'one or two minor details, the most important of which is the provision of make-before-break springs on the switching relay in the line circuit. When the switch is taken int-o use, line relay 104 operates and at its armature 105 completes a circuit for relay 106 which also operates and at armature 107 prepares the impulsing circuit. When the third digit is dialled by the calling subscriber, line relay 5 of the local selector is operated in the usual manner, thereby energizing series relay 11, which at armature 14 completes a low resistance circuit for repeating impulses by means of armature 7 at the Sametime maintaining relay 17 energized over lits upper winding while its lower winding is short circuited. Relay 53 therefore operatesfsimilarly to relay 5, relay' 59 completes an improved impulsing circuit at 'armature 62 and impulses are thus repeated at armature 55 to the'intermediate selector in Figure 3. Relay 65 is maintained energized over its upper winding during the transmission of impulses in a similar manner to relay 17. Upon the intermittent de-energiz'ation of line relay 104 a circuit is completed from earth, armature 120 and its back contact, ar-

mature 105 and its back contact, armature 107 and its front contact, winding of series relay 108, winding of vertical magnet 109 to battery. r1`he switch is thus stepped up in accordance with the digit dialled and relay 108 isenergized throughout the series of impulses, and at armature 110 prepares the circuit of the rotary magnet. Stepping relay 111 is energized in the usual manner upon the first step of the switch and at armature 112 completes a locking circuit for itself and at armature 113 prepares a circuit for the rotary magnet 114. The hunting motion of the switch takes place'substantially in the manner previously described and when a free trunk is found, for instance, that associated with contacts 125,126 and 127, switching relay 117 is operated with the usual results, among them the disconnection of line relay 104 and of the transference of the circuit through the lowerwinding of relay 65 to line relay 154 of the connector shown in Fig.. 4. Relay 154 thereupon energizes and at a1:-v

the local and incoming selectors in the manner previously described, and since there is a straight through connection by way of the intermediate selector, the relay 154 is operated similarly. Upon the lirst deenergization of relay 154, a circuit is completed from earth, armature 177 and its back contact, armature 155 and its back cont-act, armature 157 and its front contact, spring 162 and spring 160 with which it is normally in engagement, winding of relay 158, winding of vertical magnet 163 to battery. Relay 158 is operated as usual and remains operated throughout the train oit' impulses and at its armature 159 and its front contact serves to maintain its own circuit and that of the vertical magnet intact when oil' normal spring 162 engages spring 161 instead .of spring 160 as occurs upon the lirst step of the switch. Relay 158 cle-energizes 'when the sending of impulses ceases, and consequently the operating circuit responsive to the next and last series vof impulses extends to the rotary magnet as follows: earth, armature 177 and its back contact, .armature 155 and its back contact, armature 157 and its front contact, off normal springs 162 and 161, armature 159 and its baclr contact, bacl contact and armature 173, armature 179 1and its back contact, winding of rotary magnet 169 to battery. Relay 1164 is operated in parallel with rotary magnet 169 and remains operated throughout the train of impulses. At ,its armature 167 it prepares a circuit for the busy relay 170, at armature 166 disconnects the busy tone, at armature 1-65 shunts armature 171, and at armature 168 shunts armature 173. In case test Wiper 184 passes over busy lines during the rota-ry movement, relay 170 will be operated, and at armature 172 will prepare a locking circuit for itself, while the operation of armatures 171 and 173 will be ineffective since they are shunted as explained above.

Suppose in the first instance that the wanted subscriber is free when he is called; consequently when relay 164 deenergizes, busy relay 170, if previously operated, will be deenergi-zed, and a circuit will be cornpleted as follows: earth on release trunk conductor 15.2l (which is provided at armature 57 of the incoming selector), armature 172 and its back contact, upper winding of relay 174, back contact and armature 167, wiper 184, contact 187, winding of switchino; relay of the called subscribers line switch, winding` o1 stepping magnet of the line .switch to battery. Relay 174 and the switching relay are energized in series in thisl circuit, but not the magnet, and the switching relay in well lrnown mannerpar- 'tially operates its` ,armatures to clear the call-ed line ofV its normal battery and earth alternately to the lower trunk conductor so that the subscribers bell is rung interr'nitten-tly in the usual manner. 2

Wvhen the wiper relay 174 operates, the circuit of the line relay 1.54 is broken and consequently also the circuit-of the relay in vthe incoming selector, Fig. 2. This therefore releases its armatures, at armature 67 connects up the supervisory relays 82 and 88 to the upper trunk conductor extending to the connector and at arma-ture 68 connects up a retard coil 69 to supply talking battery to the wanted party. Relay 65 also atarmature 66 opens the .circuit through the upper winding of relay53 and hence also the circuit of the relay 17 in the local selector. Relay 17 on releasing, at armature 18 connects up the supervisory relays 32 and 36 and at armature 19 connects up the retard coil 20 to supply current for mainaining the line relay'53 energized over its lower winding. The circuits are now in what may be described a waiting condition, all apparatus used only during the ,setting up of the connection has been disconnected and the necessary circuits for supervision have been prepared. lVhen the called partyl replies the ringing trip relay 189 is energized in the usual manner and at its armature 191 completes a locking; circuit for itself tofreleas-e trunk conductor 152 and at armatures 190 and 192 disconnects the ringing current and connects the speaking leadsy through. Y

Upon the operation of relay 189 a circuit is completed as follow-s: battery, retard coil 69, back contact and armature 68, front contact and armature 5.5, front contact and armature 81, Wiper 93, Contact 96, lead 102, front contact and armature 121, Wiper 123, contact 126, lead 153, front Contact and armature 192, armature 181 and its front contact, Wiper 183, Contact 186, subscribers loop, contact 185, wiper182, front Contact and armature 175, armature 190 and its front contact, lead 151, Contact 125, Wiper 122, armature 118 and its front contact. lead 101, contact 95, wiper 92, armature 77 and its .frontcontact, armature 67 and its baclr contact, armature 80 and its front contact,

lower winding ot' relay 82, winding ofy re-y for relay 56, at armature 80 short circuits the lower winding of relay 82, so as' to secure a better balanced speaking circuit, and at armature 89 connects battery through the retard coil 86 to conductor 51. now completed as follows:-battery, retard coil 86, armature 84 and its front Contact, front contact and armature89, lead 51, con`l tact 42, wiper 39, armature 28 and its front contact, armature 18 and it back contact,

armature 30 and its front contact, lower.

windingv of rela-y 32, winding of relay 36 to earth. -Both relays 32 and 36 operate in this circuit, and the former at armature 33.

completes the locking circuit for itself by way of its upper winding, at armature 34 opens a point in the circuitfformaintaining relay 8 energized and at varmature 35 completes a circuit for operating Athe calling subscribers meter. Relay 36 Aat armature 37 short circuits the lower winding of relay 32 so as to balance the speaking circuit and at armature 38 closes a point inthe circuit previously mentioned for maintaining relay 8 energized. The connection has now been completely established and since itis suc-A cessful the calling subscribers rmeter has been operated to charge him accordingly. Feeding current is supplied to the calling party from-the windings of relay 5 of the first selector and to the'called party from the retard 69 and relay 88 in the incoming se lector.

The connection is released under the control of the calling party. When he replaces his receiver, a prolonged cle-energization of relay 5 is effected and it therefore opens the circuit ol relay 8. This-de-energizes after a short interval and removes earth from release trunk conductor 3thereby` releasing the line switch and relay 27 and removing earth from Contact 44 so that the trunk line is again accessible to other selectors. When both relays 5 and 8 have deenergized a circuit for the release magnet 46 is completed and the switch is restored to normal, this circuit being opened by off normal contacts 45 when the switch has returned to its normal position. The release of relay 5 also at armature 7 opens the circuit for maintaining relay 53 energized, so that this deenergizes land shortly afterwards relay 56 also. Therer upon atk armature 57 earth is removed from the release trunk conductor, whereupon re- A circuit isV lays 76 in the incoming selector 117 in the intermediate selector 189 and 174 in the connector are de-energized',.and these switches are restored to normal in the usual manner.

The case will now be considered in which the wanted partyis busy when he'is. called. In this case when the wipers of the .connectors come to rest, test wiper r184 will `find earth Ion contact 187 with which'it is inengagement, and consequently relay 170 will be energized.l Accordingly when relay 164 deenergizes, relay 170 isy locked up to the release trunk conductor over .its armature 172 and the normally closed' springs con-v f' trolled by armature l167 .and at its armature 171 it operates to disconnect the upper winding of line relay 154 and to 'connect busytone Iand busy Hash battery through a high resistance tothe linealternately. .When battery lis first removed from theupper-trunk conductor relay 65 is deenergized and the apparatusis operated to the waiting condition. When battery is again connected up, the following circuit is completed; busy flash battery, high resistance193,rback contact and armature 166, front contact and: armature 171, armature 176 and its back contact, lead 151, contact 125, wiper 122, armature 118 and its front contact, lead 101, Contact 95, wiper 92, armaturey 77 and its front Contact, armature y67 and its back contact, armature 80 .and its front Contact, lower winding of relay 82, winding of relay 88 to earth. `0w= ing to the inclusion of thehigh resistance 193 in this circuit, vonly relay 88 operates, thereupon at its armature 91 completing an auxiliary circuit for relay 56 aty armature 90 short circuiting thev lower winding of relay 82, and at armaturef89y completin the following circuit: battery, retard coi? 86, high resistance 85, front contact and armature 89,

vlead 51, contact 42,1wiper`39, armature 28 and its front'contact, armature 18 and its back contact, armature 30 and its front coni tact, lower Winding ofrelay 32, winding of relay 36 to earth.- Owing to the inclusion of the resistance 85 in this circuit, only relay 36 operates land short circuits the lower takes place. lThe operation in case a selector 'is driven to the 11th contact owing to all of a group of trunks being busy is substan.

tially the same, busy tone and busy flash bat- 4 and suppose further that a connection has been extended .over the switches shown in Figs. 1 and 2 `and 3 in the manner described above. When the intermediate vselector in Fig. r3 switches through, afcircuit completed as follows: battery, retardcoil 207,

armature 210 and its back contact, lead 202,

contact 126, wiper 123, armature 121 andv its rontcontact, lead102, contact 96, wiper 93, armature 81 and its front Contact, armature L and its liront contact, arn'izfiture 68 and its front contact, lower winding ot relay65, Jfront contact and armature 67, front contact `and armature 77, wiper 92, contact 95,'lead 101, front Contact and armature 118, wiper 122, Contact 125, lead 201, baclr contact and armature 216,norinally closed springs controlled by armature 205, Awinding of relay 204 to earth. Relay 204 operates in this circuit and at armature 206 lights the calling lamp 215, and at armature 205 completes a locking circuit. for itself dependent upon armature 209. The opening of the initial renergizing circuit :tor relay 204 opens the circuit ot' relay 65 in the incoming selector Vwhich therefore deenergizes and prepares the supervisory circuits in the manner previously described. Uponnoting the lighted condition of the lamp 215, the operator will plug into the jack whereupon the sleeve relay 208is operated. This then y at its armature `212 extinguishes the lamp 215, at armature 211 connects impedance 214 across the jack springs, at armature 210 disconnects retard 207 'fromthe lower trunk lead 202 and connects it through the high resistance 213 to the upper trunk lead 201,

at armature216 opens the initial energiz-v of relay 88 to earth. Owing to the inclusion of the resistance 21,3 in this circuit onlyrelay 88 operates, and at its armature 91 com. pletes a holding circuit for relay '56 thereby placing the release of the connection under the control of the operator, at armature 90` short circuits the lower windingct relayA 82 and at armature 89 completes a circuit including the high resistance 85 through.v relays 32 and 36 of the first selector. As previously mentioned, relay 32 cannot operate in series with this resistance, but relay 36 operates and at its `armature 38 completes a holding circuit for relay V8. In this-case also since relay 32 is not operated, no metering takes place. When the calling party has obtained the required information and hangs up his receiver, line relay tris deenergized whereupon it releases Vits armature 7, thus opening the circuit of line relay 53 in the incoming selector. This in simil-ar manner releases its armature 58 thereby opening the circuit ot' relay 204 at the opera-y tors position. This then releases andcompletes a circuit over armature 206 and its back contact, iront contact and armature 212 for the supervisory lamp 215. theirv this Aoccurs the operatorie notified that the calling subscriber has hung up, and she accordingly removes the plug thereby deenergizing `relay 208. In consequencebatteryl through retard `coil 207 is removed from the upper trunk conductor and rel/ay 88 in the incoming selector, Fig. 2, deenergizes. Upon the opening of contact 91 which then takes place, relay 56 is no longer held up, and'by releasing its armature 57 removes earth Afrom the release trunk conductor so that this switch and the intermediate Vselector are released in the usual manner. The release or' armature 89 of relay 8 8 also opens the circuit of relay 36 of the irst selector;V

in consequence of which'relay 8 is deenergized, earth is removedfrom release trunk conductor 3 and the lirst selector and 'sube scribers line switch are restored to normal.

Consider now the case in which a connection is set up by an operatorto an automatic subscriber in a distant exchange. In order to obtain a complete circuit for this connection, Figs. 6 and 7 should be substituted for Figs. 1 and 2, so that the connec` tion will thus extend through Figs. 6, 7, 3 and 4. When the calling subscriber removes his receiver, the A operator is notified in the usual manner by the lighting of the calling lamp and inserts the answering plug P into his jack J and after throwing the key K to the left or answering position ascertains his requirements. She then inserts the calling plug P2 in the jack J2 associated with a free trunk line leading to the desired exchange, the 'trunk being recognized as free if the lamp 306 is not lighted. When the plug is inserted, a circuit is closed for lamp 31 and relay 304 in series over the sleeve of 1 the plug, thelamp v306is thus lighted by the operation of armature 305. The operator then throws the key K to the right or dialling Aposition whereupon afcircuit is completed for the line relay of the-operators incoming selector as follows: battery, shunt springs 302 kof the dial, impulse springs 303,

upper contact of the spring `300 of the key-7 however, the dialling key is thrownl relay 253 operates in the circuit just described and at its armature 254 completes a circuit for release relay 256 and at armature 255 prepares a circuit acrossv the conductors 295 and 296 outgoing to the next switch. Relay 256 upon operating, at armature 257 connects earth to the release trunk conductor, at armature 258 prepares the impulsing circuit, and at armature 259 Vcompletes a circuit by wayv of back contact and armature 282l for the lower winding ofrelay 264 which relay then operates. At armature 265it connects line` relay 253 to the upper trunk con- .ductor independently of armature 279, vat

= armature 266fand 267 completes a locking,

`cuit of line relay 253 and it will deenergize a corresponding number oftimes. Upon each deenergization a. circuit is completed as follows: earth, armature 254 and yits backcoutact, armature 258 and its front contact, armature 269 and its back contact, winding of vertical magnet 270 to battery; the switch wipers are therefore raised a number of steps corresponding to the level desired. A branch of this circuit extends through relay 26() whichoperates and remains energized:V

throughout the train of' impulses since it is slow to release. Relay 260 at armature 263 completes alternative circuit for relay 264, although this is unnecessary at this point since the' circuit by way ofv armatures 259 and 282 is still closed, and atarmature 261 closes a low resistance bridge across the outgoing trunlr conductors although this also is without elect at thepresent time, since armatures 257 and its front contact, earth.

278 and 2831 have not yet been operated. Relay 260 also at armature 262 prepares a circuit for rthe stepping relay 271 which is completed as follows when off normal springs 276 close: battery, windingv of relay 271, off normal springs 276inte'rrupter contact 275, back Contact and armature 281, armature 262 and its front contact, armature Relay 271 operates in the usual manner to prepare a circuit at armature 272 for' 4the rotary magnet 274 and at armature 273 to complete a locking circuit for itself. When relay'260 deenergizes at the end of the train of impulses, the circuit of rotary magnet 274 completed by way of the normally closed springs controlled by armature 262 and the switch takes one step, whereupon stepping relay 271 is deenergized by the'opening of the interrupter contact 275. In case test `wiper 297 finds earth on the contact with which it is now inl engagement relay 271xwillbe again energized and the switch will take a further step. This operation continues until a freetrunk line is found whereupon switching relay 277 is no longer vvshort circuited andl operates, thereby at its armatures 278 and 283 connected the'upper winding of relay 264 through to. the line relay 104 of the intermediate selector. Relay 277 also 'at armature 279 prepares another circuit for line relay .253, aty armature 280 prepares circuits lfor the supervisory relay 284 .at armature 269 opens a point in the circuit of the vertical magnetand at armature 282 opens the initial energizing circuit for relay 264.

When the next digit. is dialled a number of interruptions are produced in the circuit of line relay 253 in the usual manner and it deenergizes accordingly and'by means of its contact 255 repeats the impulses to the succeeding selector, in this case the intermediate selector shown in Fig. 3. Relay -260 is energized throughout the series of im.- pulses and at its varmature 261 connects the outgoing trunk conductors together so as' to improvey the impulsing andy at its armature 263 completes a circuit through the lower winding of relay 264 so that this relay is not deenergized when its` upper winding is short-circuited by the operation of armature 261. ate the vertical magnet 270 since the armature 269 has been operated, nor can the operation of armature 262 again energize stepping relay 271 since armature 281 has been operated.

The connection is extended through the The impulses cannot now opery intermediate selector in the manner previousvly described and the remaining two. series of impulses operate the connector shown in Fig. 4in kthe usjualmanner, being repeated Assuming that the Wanted party is free when .his line is tested, the circuit through the upper winding of relay 264 is broken upon the operation of the wiper relay 174 and relay 264 deenergizes. Thereupon line relay 253 is connected over the normally closed springs controlled by armature 265 and armature 279 and its front Contact `to the lower trunk conductor 252 and hence as long as the key K1 is operated to batteryY over the shunt springs 302 and after the key is released to battery through the retard 308. Relay 264 also at armatures 266-and 267 prepares the feeding bridge for the wanted partys transmitter, this circuit including the supervisory relay 284 and retard 287.` lVhen the called party replies this circuit is completed upon the operation. of the ringing trip relay 189 and relay 284 is thenenergized. Thereupon at its armature 285 it connects the retard .coil 286v to conductor 251 and hence completes a circuit over the tip spring of jack J2, tip of plug 2, spring 300 of the key K and its normalcontact, upper right-l hand windingy of the repeating coil to earth through the winding of the supervisory relay 307. Relay 307 therefore operates its armature 309 thereby extinguishingr the lamp 310 and giving the calling operator answering supervision.

The connectionhas now been completelyv established and the two subscribers may converse, talking battery being supplied to the calling'party from the cord circuit and to the called party from the incoming selector. When they havelinished their conversation they will both replace their receivers. lVh en the calling subscriber hangs up, the usual clearing supervision is given to the A operator by the lighting of lamp 311. Vhen the called man hangs up', the circuit of relay 28/-1 is broken and it deenergizes, thereby at armature 285 opening the circuit of the supervisory relay 304 which deenergize's and lights the supervisory lamp 310. The operator upon noting the lighting of both lamps 310 and 311 removes both plugs P and P2 whereupon the circuit of line-'relay 253 is opened and all the apparatus is restored to normal in the usual manner.

In case the called man is found busy busy flash battery and busy tone will be conl nected up alternately in the connector in the be restored as previously described. It will be noted that in the casev ofthe Operators selector only one supervisory relay 2384 l:is provided since the Af'operator initiates-the metering operation and it is unnecessary standard two wire dialling circuits with'battery feed at one end (the incoming end) only and impulses transmitted by opening a loop circuit including the two talking conductors of a trunk in series. A

Further it will be noted that the impulsing circuits are prepared before the transmission of impulses has commenced and the supervisory circuits are prepared immediately after all elfectivedialling operations have ceased even if some dialling operations which are not effective due to a group of lines being busy should still be proceeding.

Having :now particularly described `Vand ascertained the nature of our said invention and in what manner thesamefis'to beperformed, we declare that what ive-claim is:

1. In an automatic ltelephone system in which the impulsesfor setting the automatic switches are sent by opening` land closing a circuit including the two talking ccnductors in series, means for subsequentlyl controlling supervision over each of the talking conductors independent of the other.

2. In an automatic telephone system in which control is exercised by the calling subscriber over the talking conductors in series until all the setting operations rhave been performed, `means for effecting circuit changes such that all subsequent control over the maintenance of the connection by the calling subscriber is exercised over one talking conductor independent of the. other.

3. In a combined manual and automatic telephone system, in which an .impulse sender is ,associated with an operators position to enable the operator to effect the settingof the automatic switches, means including a switching device in one automatic switch for reversing the battery connections to the talking conductors after the automatic switches have been operated so as to place the circuits in condition f-or the transmission of supervisory signals, each of said signalsbeing transmitted over one-*talking .conductor independent of the other. f

4. In a combined lmanualrand automatic telephone system in which an impulse sender is associated with an operators position to enable the operator to effect the setting of the automatic switches, 4a normally-open st'vitch-v l Y pendent oi said batteryv connection.

control circuit extending yto the iirst of said switches including the two talking conductors and said sender in series, means rfor preparing said switch control vcircuit by connecting said sender thereto, and means -responsive to .such operation and controlled over one talking conductor independent of the other for completing said switch-control circuit. Y n f j 5. In a combined manual and automatic telephone system in which an impulse sentier' is associated with anoperators position to enable the operator to effecty the setting of the automatic. switches, a 'normally-open switch-control circuit extending from the operators position to the irst automatic switch including the twol talking conductors and said sender in series, a preparing circuit including one talking 'conductor independent of the other, means in the first automatic switch controlled overr said preparing circuit or completing the said switch-control circuit before the sender is turned off normal, and means responsive to the turning of said impulse sender oii normal for opening said preparing circuit. n

6. In a telephone system, a trunk line eX- tending to an automatic impulse repeater, a-

train of automatic switches operated by said impulse repeater to set up ak telephone connection, a repeating relay in said repeater controlled over the two conductors of said trunk line in series during the repeating of impulses, means for setting up supervisory.

conditions in the established connection, and means for maintainingk said repeating relay energized thereafter over one talking conductor of said trunk line independent of the other. v

7. In a telephone system, a trunk line eX- tending to an automatic impulserepeater, a train of automatic switches controlled by said repeater to set up av telephone connec tion, a supervisory relay in said repeater,

vand means revertively controlled over the established connection responsive to its completion for initially connecting said supervisory relay to only one of the talking 'conductors outgoingfrom said'repeater.

8. In telephone system, an automatic impulse repeater, a trunk line outgoing from said repeater including two talking conductors, a bridge across said talking conductors free from local battery and ground connections, a train of automatic switches, means for operat-ing said .train of automatic switches to set up a telephone connection by interrupting the said bridge, means eiective subsequent to the establishment of said connection for opening said bridge, for establishing a battery connect-ion to one of said talking conductors, and for establishing a yductorq and supervisory apparatus controlled through said groundI vconnection" and inde- `9L In' a telephone system asfclaimed in vclaim 8,V in' which the ,switching device for Areplacing thel bridge with the battery' and groundconnections` includes av relay energized in said bridge by current supplied over the outgoing talking conductors during the setting upvof the-connection, means in the switch train for` deen'ergizing the said relay responsive to the' establishment' of the con- Anection by stopping'the current iow over .the outgoing conductors.v

10. In an automatic telephone system in which current for the purpose of setting the 'switches is fed Aback over the twol talking conductors yin series during the process of setting up the connection, means forsuitably alteringv the circuits so 'that current for speaking and holding purposes is fed forward over` the Asame conductorsthereafter, Vsaid altering'means c on'iprisingy contacts on a's'low acting relay energized during the setting operation by the current whichA is fed back.

ll. In an automatic telephone system in which the automatic switches are set by im pulses transmitted over a talking conductor and in which a switch-.over operation is performed to switch ther circuits from setting vconditions to talkingv and supervisory conditions responsive to the completion of the connection, a switch-over relay forperforming the said switch-over operation, means for energizing said `switch-over relay in a local circuit responsive to the transmission of the irst series of setting impulses, and means for maintaining said relay energized valternately in a local circuitvand in the setting circuit until the connection has been set up, and means for then opening the setting circuit to deenergizesaid switch-over relay. j

l2. In a telephone system, means including a trunk line and an .automatic switch for setting up a connection from a calling line to a called line of one class and for set-y ting up a connection `from the same calling line to the called line of another class, two y batteryl feed relays connected in seriesbetween one of the talking conductors of said trunkline and the exchange battery, means for operating both of said relays over the first connection, and means for operating one of said relays over the second connection and for preventing the operation of the other. v f

13. In an automatic telephone system in which setting and supervision are eected over the talking conductors under different circuit conditions, means for switching over' from setting conditions lto supervisory conditions responsive to the completion of the onnectnmA in one case and for performing an identical switch-over operation responsive to the encountering of a busy trunk group .in another case, `and means whereby supervision yfrom the calling party is trans-v f whereby supervision .from the called party is, transmitted baci; inthe direction of the calling partyvover the said other conductor independent of said one conductor.

14. Inan automatic telephone system in which the setting up of a connection through successive switching stages and supervision are effected over the talking conductors under different 'circuit conditions, means for switchingfover from setting conditions to supervisory conditions responsive to a busy condition encountered at any one of 4a pluyralit of switching staUes and means whereby supervision from the calling party is transmitted forward over the connection in the direction of the called party over one and whereby supervision from the call-ed party is transmitted back in the direction of the calling party over the said.l other conductor independent of said one con- 16. In a telephone s stein as claimed in claim 12,l a register or registering conipleted connections oi one class, and a circuit for controlling said register controlled `jointly by said relays.`

S'gned by me at London, England, this 10th day of September,192l.` f

RICHARD MERCER. i f

Signed by me at'London, England, this 10th day of September, 1924:. o

f vWILLIAM H. PAULETT.

Signed by me at London, England, this 10th day of September, 1924.

. FRANK TENCH. 

